116 



H. ater is essentially a root-dweller and probably breeds only in the 

 Scots pine, though it feeds on spruce, Douglas fir and perhaps larch 

 in newly-formed plantations, attacking these below the soil level. 

 The favourite breeding-ground of this species is Scots pine clearings, 

 though it may occur on the roots of standing dead or sickly pines in 

 high forests. Pairing may take place in the soil or in the crutch of the 

 brood-gallery and may occur before the beetles, or at any rate the 

 females, are fully mature. The female cuts out a brood-gallery or 

 mother-gallery which begins with a short., transverse, crutch-like 

 portion and is followed by the long straight gallery proper, the male, 

 if present, clearing away the detritus. Oviposition takes place in 

 the dust nibbled by the female from the sides of the tunnel, the eggs 

 being protected by shiny threads that consolidate the frass around 

 them. The eggs hatch in a period varying from a fortnight to three 

 weeks and the newly-hatched larvae start boring at right angles to the 

 mother-gallery. The cutting of the gallery and oviposition extends 

 over a period of six or seven weeks (1st May to 27th June), the average 

 number of eggs per gallery being 120. The duration of the larval 

 stage is eight or nine weeks, six or seven being devoted to feeding and 

 the remainder to resting, while that of the pupal stage is only nine to 

 eleven days, the total period from egg to adult being two to three 

 months. 



Harmful beetles associated with H. ater are Hylohius ahietis, L., 

 Pissodes pini, L., Myelophilns piniperda, L.. and Hylastes palliatus, 

 the last three being found on the upper parts of the stump, and only 

 rarely on the roots. The following useful predaceous beetles are 

 associated with H. ater: Clerus {Thanasimus) formicarius, L., a 

 northern insect found in Aberdeenshire and Perthshire but not further 

 south ; Pityophagus ferrugineus, F., a soil-dweller, also more conmaon 

 in the north ; Rhizophagus dispar, Pk., an extremely voracious species ; 

 R, ferrugineus, Pk., and R. depressus, F. ; Ips 4-pustulatus, L. ; and 

 Tachyporus chrysomelinus, L., found in enormous numbers in a clearing 

 in Aberdeenshire. Hymenopterous parasites include two Braconids 

 and a Chalcid. 



The life-history of H. paUiatus is very similar to that of H. ater, 

 except as regards its habitat, H. p)alliatus breeding and feeding above 

 the soil level on the stems and crowns of Scots pine and spruce, and 

 less commonly larch ; unlike its congeners, it may begin to feed 

 without leaving its pupal chamber. This species prefers thin bark 

 trees, 30-60 years of age, and being a bast feeder, when it occurs on 

 stumps, it bores from the cut surface directly into the cambium. 



Injurious beetles associated with H. palliatus are Myelophilus 

 piniperda, L., Pissodes pini, L., Pityogenes bidentatus, Hbst., and 

 P. quadridentatus, Htg., which occur on the stems and crowns of Scots 

 pine ; Dryocoetes autographus, Ratz., and Trypodendron lineatum, 01., 

 on the stems and cro\\Tis of spruce ; and Hylohius ahietis, L. Useful 

 insects which -associate with H. paUiatus are the same as those found 

 with H. ater, with the exception of Pityophagus ferrugineus, F. 



The life-history and habits of H, cunicularius have already been 

 dealt with [see this Review, Ser. A, v, p. 5]. 



As a forest pest, H. palliatus is of less importance than H. ater and 

 H. cunicidarius, since it infests trees at an age when they are better 

 able to overcome attack, and moreover, trees killed bv it are still 



